| /************************************************************** |
| * |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| * |
| *************************************************************/ |
| |
| |
| #ifndef _STOC_SEC_LRU_CACHE_H_ |
| #define _STOC_SEC_LRU_CACHE_H_ |
| |
| #include <hash_map> |
| |
| // __CACHE_DIAGNOSE works only for OUString keys |
| #ifdef __CACHE_DIAGNOSE |
| #include <osl/diagnose.h> |
| #include <rtl/ustrbuf.hxx> |
| #include <rtl/ustring.hxx> |
| #include <rtl/string.hxx> |
| #endif |
| |
| |
| namespace stoc_sec |
| { |
| |
| /** Implementation of a least recently used (lru) cache. |
| */ |
| template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey > |
| class lru_cache |
| { |
| struct Entry |
| { |
| t_key m_key; |
| t_val m_val; |
| Entry * m_pred; |
| Entry * m_succ; |
| }; |
| typedef ::std::hash_map< t_key, Entry *, t_hashKey, t_equalKey > t_key2element; |
| t_key2element m_key2element; |
| ::std::size_t m_size; |
| |
| Entry * m_block; |
| mutable Entry * m_head; |
| mutable Entry * m_tail; |
| inline void toFront( Entry * entry ) const SAL_THROW( () ); |
| |
| public: |
| /** Default Ctor. Does not cache. |
| */ |
| inline lru_cache() SAL_THROW( () ); |
| /** Ctor. |
| |
| @param size number of elements to be cached; default param set to 128 |
| */ |
| inline lru_cache( ::std::size_t size ) SAL_THROW( () ); |
| |
| /** Destructor: releases all cached elements and keys. |
| */ |
| inline ~lru_cache() SAL_THROW( () ); |
| |
| /** Retrieves a pointer to value in cache. Returns 0, if none was found. |
| |
| @param key a key |
| @return pointer to value or 0 |
| */ |
| inline t_val const * lookup( t_key const & key ) const SAL_THROW( () ); |
| |
| /** Sets a value to be cached for given key. |
| |
| @param key a key |
| @param val a value |
| */ |
| inline void set( t_key const & key, t_val const & val ) SAL_THROW( () ); |
| |
| /** Tests whether a value is cached for given key. |
| |
| @param key a key |
| @return true, if value is cached |
| */ |
| inline bool has( t_key const & key ) const SAL_THROW( () ); |
| |
| /** Clears the cache, releasing all cached elements and keys. |
| */ |
| inline void clear() SAL_THROW( () ); |
| |
| /** Sets the number of elements to be cached. This will clear previous entries. |
| |
| @param cacheSize number of elements to be cached |
| */ |
| inline void setSize( ::std::size_t size ) SAL_THROW( () ); |
| }; |
| //__________________________________________________________________________________________________ |
| template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey > |
| inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::setSize( |
| ::std::size_t size ) SAL_THROW( () ) |
| { |
| m_key2element.clear(); |
| delete [] m_block; |
| m_block = 0; |
| m_size = size; |
| |
| if (0 < m_size) |
| { |
| m_block = new Entry[ m_size ]; |
| m_head = m_block; |
| m_tail = m_block + m_size -1; |
| for ( ::std::size_t nPos = m_size; nPos--; ) |
| { |
| m_block[ nPos ].m_pred = m_block + nPos -1; |
| m_block[ nPos ].m_succ = m_block + nPos +1; |
| } |
| } |
| } |
| //__________________________________________________________________________________________________ |
| template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey > |
| inline lru_cache< t_key, t_val, t_hashKey, t_equalKey >::lru_cache( |
| ::std::size_t size ) SAL_THROW( () ) |
| : m_size( 0 ) |
| , m_block( 0 ) |
| { |
| setSize( size ); |
| } |
| //__________________________________________________________________________________________________ |
| template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey > |
| inline lru_cache< t_key, t_val, t_hashKey, t_equalKey >::lru_cache() SAL_THROW( () ) |
| : m_size( 0 ) |
| , m_block( 0 ) |
| { |
| } |
| //__________________________________________________________________________________________________ |
| template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey > |
| inline lru_cache< t_key, t_val, t_hashKey, t_equalKey >::~lru_cache() |
| SAL_THROW( () ) |
| { |
| delete [] m_block; |
| } |
| //__________________________________________________________________________________________________ |
| template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey > |
| inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::toFront( |
| Entry * entry ) const SAL_THROW( () ) |
| { |
| if (entry != m_head) |
| { |
| // cut out element |
| if (entry == m_tail) |
| { |
| m_tail = entry->m_pred; |
| } |
| else |
| { |
| entry->m_succ->m_pred = entry->m_pred; |
| entry->m_pred->m_succ = entry->m_succ; |
| } |
| // push to front |
| m_head->m_pred = entry; |
| entry->m_succ = m_head; |
| m_head = entry; |
| } |
| } |
| //__________________________________________________________________________________________________ |
| template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey > |
| inline bool lru_cache< t_key, t_val, t_hashKey, t_equalKey >::has( |
| t_key const & key ) const SAL_THROW( () ) |
| { |
| typename t_key2element::const_iterator const iFind( m_key2element.find( key ) ); |
| return (iFind != m_key2element.end()); |
| } |
| //__________________________________________________________________________________________________ |
| template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey > |
| inline t_val const * lru_cache< t_key, t_val, t_hashKey, t_equalKey >::lookup( |
| t_key const & key ) const SAL_THROW( () ) |
| { |
| if (0 < m_size) |
| { |
| typename t_key2element::const_iterator const iFind( m_key2element.find( key ) ); |
| if (iFind != m_key2element.end()) |
| { |
| Entry * entry = iFind->second; |
| toFront( entry ); |
| #ifdef __CACHE_DIAGNOSE |
| ::rtl::OUStringBuffer buf( 48 ); |
| buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("> retrieved element \"") ); |
| buf.append( entry->m_key ); |
| buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("\" from cache") ); |
| ::rtl::OString str( ::rtl::OUStringToOString( |
| buf.makeStringAndClear(), RTL_TEXTENCODING_ASCII_US ) ); |
| OSL_TRACE( str.getStr() ); |
| #endif |
| return &entry->m_val; |
| } |
| } |
| return 0; |
| } |
| //__________________________________________________________________________________________________ |
| template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey > |
| inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::set( |
| t_key const & key, t_val const & val ) SAL_THROW( () ) |
| { |
| if (0 < m_size) |
| { |
| typename t_key2element::const_iterator const iFind( m_key2element.find( key ) ); |
| |
| Entry * entry; |
| if (iFind == m_key2element.end()) |
| { |
| entry = m_tail; // erase last element |
| #ifdef __CACHE_DIAGNOSE |
| if (entry->m_key.getLength()) |
| { |
| ::rtl::OUStringBuffer buf( 48 ); |
| buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("> kicking element \"") ); |
| buf.append( entry->m_key ); |
| buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("\" from cache") ); |
| ::rtl::OString str( ::rtl::OUStringToOString( |
| buf.makeStringAndClear(), RTL_TEXTENCODING_ASCII_US ) ); |
| OSL_TRACE( str.getStr() ); |
| } |
| #endif |
| m_key2element.erase( entry->m_key ); |
| entry->m_key = key; |
| ::std::pair< typename t_key2element::iterator, bool > insertion( |
| m_key2element.insert( typename t_key2element::value_type( key, entry ) ) ); |
| #ifdef __CACHE_DIAGNOSE |
| OSL_ENSURE( insertion.second, "### inserting new cache entry failed?!" ); |
| #endif |
| } |
| else |
| { |
| entry = iFind->second; |
| #ifdef __CACHE_DIAGNOSE |
| ::rtl::OUStringBuffer buf( 48 ); |
| buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("> replacing element \"") ); |
| buf.append( entry->m_key ); |
| buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("\" in cache") ); |
| ::rtl::OString str( ::rtl::OUStringToOString( |
| buf.makeStringAndClear(), RTL_TEXTENCODING_ASCII_US ) ); |
| OSL_TRACE( str.getStr() ); |
| #endif |
| } |
| entry->m_val = val; |
| toFront( entry ); |
| } |
| } |
| //__________________________________________________________________________________________________ |
| template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey > |
| inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::clear() SAL_THROW( () ) |
| { |
| m_key2element.clear(); |
| for ( ::std::size_t nPos = m_size; nPos--; ) |
| { |
| m_block[ nPos ].m_key = t_key(); |
| m_block[ nPos ].m_val = t_val(); |
| } |
| #ifdef __CACHE_DIAGNOSE |
| OSL_TRACE( "> cleared cache\n" ); |
| #endif |
| } |
| |
| } |
| |
| #endif |
